The contribution that individual forest areas could make toward satisfying the conservation criteria was assessed with a new software system based on the idea of irreplaceability. The system was developed as a prototype in May 1994, using a data set from the Western Division of NSW, and was described as a way of facilitating negotiations over which areas should be taken out of commercial use and managed for nature conservation. The prototype system showed that the approach was feasible, and the software was extended and refined as part of the IAP.
Previous systematic approaches to conservation assessment have either ranked areas according to conservation priority or importance, or used area selection methods to identify sets of areas that will achieve an explicit conservation goal. The limitation of both these approaches is that they do not recognise the options that exist for constructing a system of reserves or deferred areas. For example, an area selection method might identify 50 forest compartments in a management area as being needed to achieve a particular conservation goal, but this analysis gives no information on the extent to which each of the selected compartments could be replaced with others to achieve the same goal. It cannot be assumed that the 50 selected areas are the only ones that will fulfil the conservation criteria, or that they necessarily have the highest priority for protection.
The concept of irreplaceability recognises that there are usually many ways of constructing a system of protected areas. Some areas cannot be replaced without compromising the conservation goal, either because they contain unique features, because they contain so much of a feature that other areas cannot compensate for their loss, or because the conservation goal specifies that all occurrences of one or more of the features they contain must be reserved or deferred. Other areas are replaceable to varying degrees. There might be one or a few choices for some areas and hundreds of choices for others.
Irreplaceability can be defined in two ways:
Areas can be given values that range from 1 (totally irreplaceable) to zero (not containing any features that are needed to achieve the conservation criteria). In between these two extremes, values reflect the number of replacements that exist for any particular area. The pattern of irreplaceability in a region depends strongly on the conservation criteria that are set for the region. If the target areas for forest types or species are reduced, the irreplaceability of the individual areas will tend to decrease.
A computer model has been developed to predict the irreplaceability of the forest estate (see Section 2.5.2). The various studies described in Chapter 3 provide the basic data inputs to the model in the manner depicted in Figure 2.3.
Previous approaches to estimating the irreplaceability of areas involved stepwise calculations based on the rarity of the features that the areas contained. These methods have now been replaced by a statistical estimation approach that has yet to be published, but which will be in manuscript form by about August 1996. The new approach estimates the extent to which the options for achieving the goal for each feature in the data set will be reduced if a particular area is not available for nature conservation. The values for each feature are then combined to give the overall irreplaceability of the area. The new approach has several advantages over previous ones.
Two examples are summed irreplaceability (the sum of all the feature irreplaceabilities) which indicates how many features the area is important for, and weighted average irreplaceability which indicates how much of a compartment is made up by highly irreplaceable forest types.
The IAP is required to assess both the conservation values and wood resource values of thousands of State Forest compartments throughout eastern NSW to decide which ones will be deferred pending final decisions on a CAR reserve system and which ones will support a sustainable timber industry.
Figure 2.3: Inputs to conservation planning software
Irreplaceability provides a useful guide for conservation decisions because it indicates the likelihood that a particular compartment will be needed as part of a CAR reserve system.
If irreplaceability is to be used most effectively in conservation planning, it needs to be part of an interactive software system. An interactive system is necessary because a simple map of irreplaceability only displays the options that exist for achieving a conservation goal at one point in time. As some of the mapped compartments in a forest region are reserved or deferred, the pattern of irreplaceability of the remaining compartments will change to some extent because some or all of the features they contain will have been represented in the developing network of deferred or reserved areas. An interactive system allows irreplaceability to be recalculated each time a decision on a compartment is made, therefore presenting the users with the most up-to-date picture of conservation options in the region. In the same way, an interactive system can recalculate and display the extent to which specific conservation criteria have been achieved and display the characteristics of one or more selected areas. This recalculation of irreplaceability also minimises unnecessary duplication of features in deferred or reserved areas.
The current conservation software consists of three main components:
These components exchange information during the negotiation process. WinERMS is a user-friendly GIS with many display and analytical functions that can be called on by the conservation software. Similarly, an existing data base management system can be used effectively without the need for special-purpose programming.
All data used by the conservation planning software are linked to a land unit layer containing the boundaries of State forest compartments, flora reserves, fauna reserves, national parks, nature reserves, vacant crown land and other tenure classes. These land units are placed into three categories:
Irreplaceability takes into account the contribution of all protected areas towards meeting targets. The model then calculates an irreplaceability index for all remaining State forest compartments that represents the contribution of individual compartments towards meeting conservation goals.
This land unit layer in the GIS was overlaid with data on the forest types and species to be considered in negotiations in each negotiation area ( Figure 2.2). A data matrix was then produced which lists the area or number of occurrences of each feature in each tenure unit. The conservation software then calculated the irreplaceability of each State forest compartment based on its contribution to meeting the targets for all features combined.
The way that this model is used in the negotiation process is described in Section 2.8.